1. Technical Field
The exemplary embodiment relates to a medical diagnostic imaging apparatus, a medical image processing method, and a computer program product.
2. Description of the Related Art                Recently, with advancement of scanning techniques and image processing techniques, it has become possible to take images of various regions of a patient (an object), at various positions and from various angles, with medical diagnostic imaging apparatuses such as magnetic resonance imaging (MRI) apparatuses and computed tomography (CT) apparatuses. For example, JP-A 2003-210430 (KOKAI) describes a technique for easily taking sectional images of a centrum, such as vertebra and lumbar vertebra, taking images of which has been heretofore considered to be difficult due to a three-dimensionally curved shape.        
In such medical diagnostic imaging apparatuses, a coordinate system having three directions, that is, vertical, horizontal, and anteroposterior, centering on the apparatus, is defined to indicate a position and an angle for using the apparatus. Such a coordinate system is specific to the apparatus for which it is defined, so that it is referred to as an “apparatus coordinate system”. However, because the patient is scanned in various postures and directions, a coordinate system, which is separate from the apparatus coordinate system, that is based on the posture and the direction of the patient is preferable. Therefore, a variable coordinate system determined by the posture of the patient (supine position (face up), prone position (face down), right decubitus position, and left decubitus position) and an insertion direction into the apparatus (from head, from feet) is defined. Because the variable coordinate system is uniquely determined based on the posture of the patient at the time of scanning, such is referred to as a “patient coordinate system”.
Depending on the type of medical test, a plurality of regions needs to be diagnosed with respect to one patient, and an image of each region is required. However, if each region is imaged separately, the total time required for scanning increases, and a burden on the patient to be scanned becomes large. Therefore, a plurality of regions is generally scanned at one stretch by setting a wider range for scanning to shorten the time. In this case, the directions of the regions in the taken image are indicated based on the same patient coordinate system.
At the time of diagnosing each region, however, if the direction of the region projected on the image is indicated based on the patient coordinate system, interpretation of radiogram becomes difficult. Normally, when each region is diagnosed, visual inspection is performed from multilateral directions on the basis of directions (vertical, horizontal, or anteroposterior directions) specifically determined for each region from an anatomical point of view. The direction, which becomes a basis, does not always agree with the direction indicated by the patient coordinate system.
This problem is particularly noticeable, for example, when a patient who cannot lie down with his body, upper limbs (arms), and lower limbs (legs) being stretched is scanned, or when scanning is performed with a region, which tends to be inclined in various directions with respect to a body axis even in the natural posture, such as legs, being included in the scanning range.
Thus, there has been a need of a medical diagnostic imaging apparatus, a medical image processing method, and a computer program product that can display an image together with the directions specifically determined for each region from an anatomical point of view.